1. Field of the Invention
The present invention generally relates to semiconductor substrate processing systems. More particularly, the present invention relates to a gas valve for pulsing of one or more gases used in a semiconductor substrate processing system.
2. Description of the Related Art
In cylindrical film processing, for example, atomic layer deposition, atomic layer etch or other repetitive, thin film deposition or etch process, is desirable to provide rapid and precise cycling of process gases to improve the production worthiness of processing systems. In this regard, valves that may reliably inject small amounts of materials at rapid rates are needed. Some current and desired feature cylindrical layer deposition processes will require injection sequences wherein a single pulse may be as short as a few tens of milliseconds and be separated from an adjacent pulse by a few tens of milliseconds. Providing such pulses of gas using conventional solenoid or pneumatically operated valves have not proven desirable for this use due to insufficient responsiveness, i.e., long cycle times, failure to shut off cleanly, high rate of particulate generation and poor reliability and short service life. These deficiencies lead to sub-optimal physical properties of the positive films, short service life and high maintenance frequencies.
Therefore, there is a need for a valve for pulsing gas during cylindrical processes such as atomic layer deposition and the like.
The present invention is a reciprocating gas valve for pulsing gases (or gas mixtures). The inventive gas valve comprises a plurality of gas inlet ports and one gas outlet port that are periodically engaged in fluid communication by a reciprocating selector plate. The selector plate comprises at least one timing slot to establish and terminate a flow of each gas (or gas mixture). In one embodiment, the inventive gas valve produces pulses having a duration of about 50 to 300 msec of three gases. In one application, the invention is used for pulsing reactive precursor and purge gases during an atomic layer deposition process performed in a semiconductor substrate processing system.